Effects of grossly over pitching yeast ?

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Nick_D
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Effects of grossly over pitching yeast ?

Postby Nick_D » Tue Sep 05, 2017 5:58 am

I'm still alive, and still suffering the same issues anytime I try to brew with even the most conservative lager fermentation scheme. Namely, underattenuation, and boat loads of acetaldehyde and diacetyl. I've tried different yeasts, shaken starters, stirred starters, pure O2 with flow meter at pitching, sterile air pumped for several hours at pitching. Fermenting warm (~ 10 C), cold. Raising temp for the classic D-rest even. Yeast nutrients, including the fabled Servomyces.

My FFT show good attlenuation (e.g. 1.048 - 1.008 or better). My ferm temp probe is calibrated. My wort ph is good (~ 5.2 into fermenter). No O2 meter yet.... but several hours of air through an air stone ought to get things up and away.

So over pitching. My last batch I tried was 10 liters. I pitched approx 170 ml of super dense slurry. Too much? FFT was 1.009 (mash temps were a bit messy), but the batch got stuck at 1.0125 ish (bottle conditioning/spunding).

I've been so concerned with getting 'enough' yeast, thinking this is the issue (i.e. not enough) that it occurs to me I may have been pushing the wrong direction. As anecdotal evidence of this, I did a Dunkel a long way back, and pitched assuming approx 4 billion cells per ml of dense sediment. This beer turned out well, albeit very sweet due to using too much munich II (100%).

A very subjective question. How much acetaldehyde and diacetyl is in your beers at transfer ? For me, I can't even taste the malt, or hop character -it's that bad.

My plan is to direct pitch one vial to 10 liters of wort (in case my starter method is doing harm), and aerate with sterile air for 5 or so hours. See where that gets me. It will be many magnitudes less yeast than I've been pitching.

Sorry for the long post, as ever. I appreciate all of your past advices, and appreciate your patience.

Nick
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Re: Effects of grossly over pitching yeast ?

Postby wobdee » Tue Sep 05, 2017 8:20 am

Does this only happen when you spund? Sounds like your stalling out during transfer for some reason. Maybe you need a little more time or higher spunding temp?

I've only spund a few times and found it not worth it for my smaller batches, I ferment to FG in 8-9 days at 8c then slowly drop to lagering temp then transfer to keg and force carb. My transfer sample always seem clean tasting but there is little yeast in suspension. I pitch about 250-300ml slurry for 11 liter batch and my FG is almost always the same as my FFT, sometimes 1 point higher.
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Nick_D
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Re: Effects of grossly over pitching yeast ?

Postby Nick_D » Tue Sep 05, 2017 11:18 am

wobdee wrote:Does this only happen when you spund? Sounds like your stalling out during transfer for some reason. Maybe you need a little more time or higher spunding temp?

I've only spund a few times and found it not worth it for my smaller batches, I ferment to FG in 8-9 days at 8c then slowly drop to lagering temp then transfer to keg and force carb. My transfer sample always seem clean tasting but there is little yeast in suspension. I pitch about 250-300ml slurry for 11 liter batch and my FG is almost always the same as my FFT, sometimes 1 point higher.


Hey Wobdee, yeah, when I transfer to spund (keg or bottles). Transfer as everyone else, about 4 points above FG. I've tried bumping the temp right up to 20 C after the transfer to spund, and it's basically the identical result, regardless. It's weird. It goes a couple of points, then stops, leaving all the by products. Totally undrinkable. Even when left to cleanup for a month. It's totally static, no change.

When you say 250 - 300 mls of slurry. Do you mean that amount of solid yeast ? or is that a loose slurry ? My recent pitch was the entire yeast cake of a 10 liter previous batch (itself a non successful brew). I remember reading someone here getting two pitches of yeast out of collected slurry..... so either my leftover yeast cake is abnormally small (Itself a point of enquiry), or I'm over pitching ?

As an experiment, I have a 10 liter batch that I haven't transferred at all, maturing (hopefully) on the yeast cake at 20C. wy2206 fermeted at 8.5 C, raised to 20 C with 4 points remaining. I just want to see if left long enough on the whole cake, wheather it cleans up the fermentation by-products. I don't care about the potential autolysis etc.... just want to see if I can get the damn thing to finish ! I'll bottle straight from the fermenter into bottles dosed with the appropriate amount of dextrose.

I've seen Nico mention one vial to 10 liters if aerated correctly will do the trick. I'm keen to try that next to see what result I get.
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Re: Effects of grossly over pitching yeast ?

Postby wobdee » Tue Sep 05, 2017 11:48 am

Nick_D wrote:
wobdee wrote:Does this only happen when you spund? Sounds like your stalling out during transfer for some reason. Maybe you need a little more time or higher spunding temp?

I've only spund a few times and found it not worth it for my smaller batches, I ferment to FG in 8-9 days at 8c then slowly drop to lagering temp then transfer to keg and force carb. My transfer sample always seem clean tasting but there is little yeast in suspension. I pitch about 250-300ml slurry for 11 liter batch and my FG is almost always the same as my FFT, sometimes 1 point higher.


Hey Wobdee, yeah, when I transfer to spund (keg or bottles). Transfer as everyone else, about 4 points above FG. I've tried bumping the temp right up to 20 C after the transfer to spund, and it's basically the identical result, regardless. It's weird. It goes a couple of points, then stops, leaving all the by products. Totally undrinkable. Even when left to cleanup for a month. It's totally static, no change.

When you say 250 - 300 mls of slurry. Do you mean that amount of solid yeast ? or is that a loose slurry ? My recent pitch was the entire yeast cake of a 10 liter previous batch (itself a non successful brew). I remember reading someone here getting two pitches of yeast out of collected slurry..... so either my leftover yeast cake is abnormally small (Itself a point of enquiry), or I'm over pitching ?

As an experiment, I have a 10 liter batch that I haven't transferred at all, maturing (hopefully) on the yeast cake at 20C. wy2206 fermeted at 8.5 C, raised to 20 C with 4 points remaining. I just want to see if left long enough on the whole cake, wheather it cleans up the fermentation by-products. I don't care about the potential autolysis etc.... just want to see if I can get the damn thing to finish ! I'll bottle straight from the fermenter into bottles dosed with the appropriate amount of dextrose.

I've seen Nico mention one vial to 10 liters if aerated correctly will do the trick. I'm keen to try that next to see what result I get.


Sounds frustrating. My slurry is probably somewhere in between solid and loose, roughly half the yeast cake. I also use Brewers Friend yeast calculator for my recipes. I keg the night before brewday so my slurry is super fresh as well and takes off within a couple hours. How old is your slurry?

Maybe try the Nico approach, personally I like to use 1 pack of 2124 per gallon, no starters and then reuse slurry for 10 or so generations until starting over again. Always have great attenuation with this method.
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Re: Effects of grossly over pitching yeast ?

Postby Nick_D » Tue Sep 05, 2017 12:32 pm

wobdee wrote: Sounds frustrating. My slurry is probably somewhere in between solid and loose, roughly half the yeast cake. I also use Brewers Friend yeast calculator for my recipes. I keg the night before brewday so my slurry is super fresh as well and takes off within a couple hours. How old is your slurry?

Maybe try the Nico approach, personally I like to use 1 pack of 2124 per gallon, no starters and then reuse slurry for 10 or so generations until starting over again. Always have great attenuation with this method.


Frustrating indeed. 2 years, and god knows how many hundreds of liters dumped :oops:

So I'm suspecting, from your mention of using half the yeast cake, that pitch rate may definitely be a factor as suspected. I think the slurry for the current batch was about 1 week in the fridge. Took off very fast. Suspiciously fast, when compared to ales I do with dry yeast. No lag time. went from 1.047 to 1.012 in 6 days. The previous 10 liter batch was from a 2.5 liter starter from a fresh pack. I always worry about the health/yeast count of my starters (for lagers anyway, never had an issue with ales). Hence why pitching a fresh pack without starter will at least rule that out of the equation.

It will be interesting to measure the yeast cake from the current batch. Suspect it will be barely larger than what was pitched.... which can't be a good thing (i.e. minimal growth of fresh new yeasties).
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Re: Effects of grossly over pitching yeast ?

Postby Techbrau » Tue Sep 05, 2017 1:11 pm

If you have had that many ruined batches over so long I think you are doing something fundamentally wrong with your process that you are unaware of.

Next time just try two packets of rehydrated dry W34/70 to establish a baseline. Depending on the results you get with that you can narrow down the list of possible causes.
If you always do what you've always done, then you'll always get what you've always gotten.
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Re: Effects of grossly over pitching yeast ?

Postby Nick_D » Tue Sep 05, 2017 2:11 pm

Techbrau wrote:If you have had that many ruined batches over so long I think you are doing something fundamentally wrong with your process that you are unaware of.

Next time just try two packets of rehydrated dry W34/70 to establish a baseline. Depending on the results you get with that you can narrow down the list of possible causes.


Hey Tech. Yeah, agreed. It must be something fundamental. I've gotten lost in the forest over all this time. Been planning an Oktoberfest party for 2 years..... My friends have given up on me !

I like your thinking. 2 packs 34/70 for 10 liters of wort? Aerate for several hours as per normal? This seems a good intermediary step before going back to liquid yeast.
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Re: Effects of grossly over pitching yeast ?

Postby Techbrau » Tue Sep 05, 2017 5:55 pm

One pack for 10 liters. Strictly speaking dry yeast does not really require aeration as it is grown aerobically in a medium whose glucose content is below the Crabtree threshold, allowing the ergosterol content of the yeast cells to grow to as much as 5% by dry weight (anaerobic growth will only ever result in about 1%). The cells have enough sterols to divide at least 4-5 times without requiring any oxygen, and 4 divisions is approximately what you need to get from a single packet of yeast to reach maximum cell density (about 200 billion cells per liter) for 10 liters of wort. That said it may still be beneficial to aerate a bit.

If you're blowing air through your wort for several hours straight and not having foam overflow your fermenter I have to wonder if you're getting much air in there at all, which could explain the problems you're having.
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Re: Effects of grossly over pitching yeast ?

Postby Nick_D » Wed Sep 06, 2017 12:37 am

Techbrau wrote:One pack for 10 liters. Strictly speaking dry yeast does not really require aeration as it is grown aerobically in a medium whose glucose content is below the Crabtree threshold, allowing the ergosterol content of the yeast cells to grow to as much as 5% by dry weight (anaerobic growth will only ever result in about 1%). The cells have enough sterols to divide at least 4-5 times without requiring any oxygen, and 4 divisions is approximately what you need to get from a single packet of yeast to reach maximum cell density (about 200 billion cells per liter) for 10 liters of wort. That said it may still be beneficial to aerate a bit.

If you're blowing air through your wort for several hours straight and not having foam overflow your fermenter I have to wonder if you're getting much air in there at all, which could explain the problems you're having.


ok cool, so this will take both yeast health, and oxygenation/aeration out of the equation. That will certainly help to narrow it down, based on my result. Thanks !

Actually, I've had quite a lot of issues with foam..... I run the aquarium pump through a HEPA filter and 2 micron stone. My plastic fermenter is good for 30 liters though, so even a 20 liter batch has headspace for foaming. I would normally open it up every hour or so and knock the foam down. Unattended aeration has resulted in some big messes however :?

I've also used pure O2 on a 1 micron stone, with a flow meter. 1/4 liter per minute for 4 minutes for a 20 liter batch. I've tried less, more. None. Shaking only. Running the aquarium pump for an hour. Right up to running it for 24 hrs. Exact same result each time.

I have now swapped my flow meter over to my aquarium pump setup, so that I can control aeration, without excessive foam issues. I'm yet to give this setup a proper go.

I will proceed as suggested with dry yeast, and report back ! thanks for taking the time to help me out. I really appreciate it.
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Re: Effects of grossly over pitching yeast ?

Postby Ancient Abbey » Wed Sep 06, 2017 8:59 am

Nick_D wrote:So over pitching. My last batch I tried was 10 liters. I pitched approx 170 ml of super dense slurry. Too much? FFT was 1.009 (mash temps were a bit messy), but the batch got stuck at 1.0125 ish (bottle conditioning/spunding).

No, that's not too much. I regularly pitch 400-500ml of dense slurry for a 20L batch.

Nick_D wrote:A very subjective question. How much acetaldehyde and diacetyl is in your beers at transfer ? For me, I can't even taste the malt, or hop character -it's that bad.


None. The one thing I noticed when I switched to the Narzis cold profile was that acetaldehyde and diacetyl were below tasting thresholds, with very rare exceptions. I get a lot of honey, indicating 2,3 pentanedione instead of 2,3 butanedione. The lower and slower growth rates should reduce the rate of production of these by-products and reverse the levels of VDK's during fermentation. At the same time, the yeast are cleaning them up before a big peak of them are noticed in the flavor. This suggests to me that you are getting too much growth, and it is growing too fast. this might be helpful:

http://onlinelibrary.wiley.com/store/10 ... ac6ba59180

Nick_D wrote:My plan is to direct pitch one vial to 10 liters of wort (in case my starter method is doing harm), and aerate with sterile air for 5 or so hours. See where that gets me. It will be many magnitudes less yeast than I've been pitching.

Over-aeration can be a major contributor to acetaldehyde. If using fresh, healthy and highly viable yeast, then as a general rule of thumb you shouldn't have to aerate longer than it take to fill the top of the fermenter with foam. If you ferment small batches in big fermenters, then this rule won't apply. That said, contamination also explains all of your by-product issues. Do you ever keep the batches long enough to see if they go funky, or do you just dump them right away? Are you sure everything you are using is sanitized? Aeration stones and tubing are often where people mess up their batches. Be sure to use 70% ethanol or boiling water as Star San won't kill Sacc or Brett.

I agree with Tech, start with packets of 34/70 and do a split bitch (or two batches). Pitch one with a single packet, pitch the second with 2 packets. Be sure to rehydrate them @100-105F using sterile water and a product call Go-Ferm. It will supersaturate the yeast with nutrients as they rehydrate, and since it lacks DAP it will not reduce viability. For these two trials, skip aeration and eliminate this variable as a source of contamination altogether.

http://www.scottlab.com/product-102.aspx

Also, in the empty container that had your yeast, fill it halfway with boiled wort (cooled) and let the yeast in there ferment out the wort. If you are using a FFT, then you can use this yeast too. If for some reason you do get off-flavors, then you can use this when it comes time to spunden. Simply rouse this little bit of really healthy yeast and pitch it as krausen when you transfer to spund. Then, wait....and wait.... ;)
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